I know that I can gain 16000 gamer points aday but they don't do anything. I have earned over a million of them. I'm in a faction and they have the seasons and you are supposed to earn yor 16 k aday so your faction gets in the top 10 top 100 etc... but there seems no point to that either. you get no notification when the season ends, there is no notification of what rank your faction was and you get no rewards.....
It's a prize for 'who can spend the most time on Zombie Slayer' Kano has mentioned that in the future there will be additional involvement with factions, so maybe the GP's will come into use then? I'm not part of a faction anymore so I don't give a damn about GP's, if I get them it's purely by chance.
Gamer points are in beta and will be used in coming features in the game. Currently if you're part of a Faction, your points contribute to the Faction's success in the weekly seasons. Season winners will receive Trophies and will be featured on the Leaderboard. More achievements and unlocks to come